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Results of a long-term selection experiment for lean tissue growth in the pig.

Abstract

An account is given of a pig selection experiment begun in 1965 at the INRA artificial insemination center of Rouille (Vienne) France. Altogether 20 successive Large White boar generations (1965-1984) have been compared, namely 179 boars tested on 5985 progeny from 1966 to 1985. The boars were selected on a performance-test index including growth rate and backfat thickness. Selection responses were measured for growth, feed efficiency, carcass traits and meat quality, by using a "repeat-sire" design and applying mixed model methodology (except for feed efficiency measured on a pen basis). Estimated annual genetic trends over boar generations are 6.4g lean/day (P^-.001) and -.30 kg feed/kg lean (P^.,01). Daily feed intake has been slightly increased (H: .1) and an unfavourable indirect response in meat colour (P ^ .001) is to be noted. Higher responses were generally observed over the second half of the experiment, as expected from the increase in boar selection intensity. Also, generally lower responses were obtained over dams, compared to sires of the same year, though the lag between them tended to become smaller in the more recent years. Those results are discussed in relation to the testing and selection system applied in the experiment.